<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    document.write("<select>");
    for(i=1;i<=12;i++){
        document.write("<option>"+i+"月</option>")
    }
    document.write("</select>");
    document.write("<select>");
    for(i=2;i<=28;i++){
        document.write("<option>"+i+"</option>")
    }
    document.write("</select>");
    document.write("<select>");
    for(i=3;i<=31;i++){
        document.write("<option>"+i+"</option>")
    }
    document.write("</select>")

</script>

</body>
</html>